SU802296A1 - Method of preparing homopolymers and shock-resistant styrene copolymers - Google Patents

Description

one

This invention relates to the preparation of homopolymers and impact copolymers of styrene.

Polystyrene plastics are widely used in construction, engineering, instrument making and many other areas.

A known industrial process for the production of polystyrene and impact polystyrene by bulk polymerization of styrene or its mixture with elastomers. When implementing this method, the heat of reaction is removed through the heat exchange surfaces embedded in the reactor and by means of inverse condensers l. However, to achieve a high monomer conversion, the process is carried out for ten hours with a gradual (stepwise) increase in the polymerization temperature. Since the viscosity of the reaction mass increases dramatically as the concentration of the polymer obtained increases, the process ends at high temperatures (220-240 ° C), which significantly affects the properties of the final product, increasing its polydispersity and deteriorating its quality.

Closest to the invention is a method for the polymerisation of styrene or its mixture with polybutadiene, which is carried out with the addition of an inert diluent to the reaction medium in an amount of 1-20 parts by weight. per 100 weight. including the raw material, mixed with the reaction mass and forming with it a homogeneous molecular solution 2.

Cycloaliphatic and aromatic hydrocarbons (benzene, toluene, ethylbenzene, cyclohexane) are used as diluents. The temperature of the reaction medium is 107-219 ° C to maintain the polymerized mixture in a fluid state.

However, this method has a number of significant drawbacks.

1. The applied system somewhat facilitates removal of the reaction heat and reduction of the viscosity of the medium for the top of the final reactor, but it does not solve the main task of heat removal of the reaction

masses and overcoming high viscosity systems for high polymer concentrations.

2. The solvent in the final reactor is present in the boiling phase of the upper layers of the reaction mass, as a result of which the heat is removed mainly from the surface. Reliable heat removal of the reaction from the depths of a highly viscous mass is practically impossible in this case. . 3. A certain decrease in the viscosity of the medium when using such a small amount of solvent is achieved by maintaining a sufficiently high temperature of the mass to ensure its fluidity; therefore, there is no possibility of obtaining a homogeneous product with a given quality throughout the whole process. 4. The solvent used reduces the molecular weight of the product due to the chain transfer reaction and, therefore, its presence in the prepolymerization zone is undesirable. 5. The solvent content in the reaction system is strictly regulated (as a large amount of it reduces the strength of the product and promotes the back mixing of the reaction mixture). 6. Polymerization is carried out in a displacement column reactor with a laminar downward flow, in which up to 6 or more built-in heat exchange surfaces are used to increase the fluidity of the mass and heat removal. The purpose of the invention is to significantly reduce the viscosity of the reaction medium with simultaneous removal of the heat of reaction to obtain a homogeneous product improved properties and simplification. technological design of the process This goal is achieved by the fact that the process is carried out in a gas-liquid emulsion created by the supply of gas or a mixture of gases that do not mix with the reaction mass. Forming a heterogeneous system provides an intensification of mass transfer and heat exchange processes, obtaining a product with a narrow molecular weight distribution. Creating a gas-liquid emulsion by supplying a large flow of the component (100-200 parts by weight or more per 100 parts by weight of the raw material versus 2-10 parts by weight of the prototype) reduces the viscosity of the medium with complete removal of the Heat of Reaction. The implementation of the process in such conditions eliminates the need to use any heat exchangers, which greatly simplifies its design and creates real conditions for the directional synthesis of the polymer with exceptional properties (uniformity, mono-distal distribution, high impact and breaking strength). The process of polymerization or copolymerization of styrene with elastomers is carried out in a cascade of 3-4 ideal mixing reactors under an overpressure of 8–60 kg / cm and at a temperature of 120–160 ° C using a hydrocarbon component or inert gas to create a gas-liquid emulsion., For example, ethene, ethylene, propane, propylene, butene, butylene, pentene, isopentane, nitrogen, or mixtures thereof. The cascade mixing reactor scheme used makes it possible to obtain a highly concentrated product at the outlet of the polymerization reactor unit (90-93%). End processing of this product - dyeing, stabilization, devolatilization, granulation, etc. - can be carried out either directly, directly in a vacuum mixer, or in a vacuum KciMepe, followed by extrusion. Process technology is shown in the drawing. The invention is illustrated by examples. Example 1. The homopolymerization of styrene is carried out in a cascade of reactors 1,2 and 3 of mixing at a temperature. Styrene from tank 4 is fed by pump 5 to reactor 1 in an amount that provides a predetermined monomer residence time in the system (about 6-8 hours). The reactors are equipped with ribbon agitators and are equipped with thermostatic jackets, into which water vapor is fed under pressure at the equilibrium temperature in the reactors. The polymerization is carried out in the presence of an inert component, propane. As a result of polymerization, the following polystyrene concentrations in styrene are set in the reactors: in the reactor 1 40-45%, in the reactor 2 60-65%, in the reactor 3 85-87%. Removal of the polymer in the cascade reactors is, kg / mh: in the reactor 1260 2150 350 The average polymer removal per unit of reaction volume (reactor unit only) is 180. A gas-liquid mixture consisting of concentrated polystyrene in the monomer and gaseous propane diluent saturated with styrene vapor,. sent to separator b, where the polystyrene solution is concentrated to 90-93%. The gaseous phase from the separator is condensed in the refrigerator 7 and recycled to the reactors. A highly finished 90-93 wt.% Polystyrene solution from the separator is sent to a screw aggregate in which the complete degassing of polystyrene occurs under vacuum and the final processing of the product. Gas unloading for phase from a screw machine condensates in the refrigerator 8g. Condensate is collected in collector 9 and sent for purification, and then to the feed tank. The pressure in the reactors is set based on the condensation of the circulating gas (25 kg / cm). The loss of inert liquid gas is replenished pump 10 on the level in the tank 11. Commercial polystyrene with stabilizer and dye added if necessary is obtained in the form of granules.

Example 2. The preparation of polystyrene is carried out according to Example 1. Liquefied ethane is used as an inert component, the process pressure is 60 kg / cm.

Example 3. The production of polystyrene is carried out similarly to that described in Example 1. Propylene is used as the inert component, the process pressure is 20 kg / cm,

Example 4. The preparation of polystyrene is carried out as described in Example 1. Butane is used as an inert component, the process pressure being 16 kg / cm.

Example 5. The preparation of polystyrene is carried out according to example 1. Ethylene is used as an inert component, the pressure in the system is 60 kg / cm

Example 6. The preparation of polystyrene is carried out according to example 1. As the inert component with butylene, the pressure in the system is 10 kg / cm.

Example 7. The preparation of polystyrene is carried out according to Example 1. Liquid nitrogen is used as an inert component, the system pressure is 60 kg / cm.

Example The preparation of polystyrene is carried out according to Example 1. Pentane is used as the inert component, the pressure in the system is 5–8 kg / cm 2.

Example 9. The preparation of polystyrene is carried out according to example 1. Isopentane is used as an inert component, the pressure in the system is 0–8 kg / cm. .

Table 1 shows the main physico-mechanical parameters of the proposed homopolymer and polymer obtained by the prototype.

25

Table

The residual monomer content,

% not less

Impact viscosity on samples, kgf / cm, not less:

without a cut

notched

Destructive stress at

stretching, kgf / cm, not less

Relative lengthening at Below are examples, illustrati. that produce high-impact styrene polymers by copolymerizing monomer with elastomers. Example 10 Styrene copolymerization is carried out in a cascade of mixing reactors at a Crumb temperature of cis-polybutadiene rubber (content of cis form 90-95%) of the brand intense PA-55 is mixed with a screw machine 12 and finally dissolved in tank 13 (concentration 6-10%) at a temperature of 30-60 C. Further polymerization of the prepared solution of elastomer in styrene is carried out0, 3-0.5

27 1.8-2.5

385-450 are similar to the process for producing a styrene homopolymer. Ethylene is used as the inert component, the system pressure is 60 kg / cm. Example 11 High impact polystyrene is prepared according to Example 1. Liquefied process oil is used as an inert component — iTa; the system pressure is 20 kg / cm. Example 12 Production of high impact polystyrene is carried out according to example 1, butene is used as the inert component, pressure in the system is 16 kg / cm.

Example 13. Preparation of high impact polystyrene is carried out according to Example 1. Ethane is used as the inertial component, system pressure is 40 kg / cm.

Example 14: Preparation of high impact polystyrene is carried out according to Example 1. Butylene is used as an inert component, the pressure in the system is 10 kg / cm.

Example 15: Preparation of high impact polystyrene is carried out according to Example 1. Propane is used as an inert component, the pressure in the system is 30 kg / cm.

Take p1b. The preparation of impact polystyrene is carried out

Retention of residual monomer,

% no more

Impact viscosity on specimens

notched, kgf / cm, not less

Destructive stress at

stretching, kgf / cm no less

Relative elongation at the proposed method allows to obtain ultrastrong grades of impact-resistant polystyrene by graft copolymerization with an elastomer suitable for processing by any of the methods known in the art, as well as styrene copolymers with various monomers (NAC, etc.). Thus, the proposed method has the following advantages: 1. Reducing the viscosity of the reaction medium by creating a gas-liquid emulsion in the reaction volume. So, at a temperature of 140 ° C and a conversion of 40% - from 10 SP, at a temperature of 155 ° C and a conversion of 80% - from, 5 to. 2. Increasing the speed of the polymerization process (160-180), with relatively low temperatures and a monomer conversion of 85-90%, which allows you to create a highly productive unit of small volume, and you get a high-quality product.

according to example 1. A foam is used as the inert component. tang; system pressure 8 kg / cm I

Example 17. The preparation of impact polystyrene is carried out according to Example 1. Isopentane is used as an inert component, the pressure in the system is 8 kg / cm.

Example 18. Preparation of high impact polystyrene is carried out according to Example 1. Nitrogen is used as an inert component; system pressure is 60 kg / cm.

In tab. 2 shows the main physico-mechanical properties of impact polystyrene, synthesized according to the method described in the prototype and according to the invention. T a b l i

c a

Claims (2)

1. US patent 3129199, cl. 260-880,1964. 2.Patent UK No. 1063603 cl. C 3 G, 1967 (prototype). (az5o8otey K ieKjfjfflr CmUjeoA entem / ff P.etiro